Differential modulator



Aug. 24, 1926. 1,597,323

J. MASSOLLE ET AL DIFFERENTIAL MODULATOR Filed March 30. 1921 3 Sheets-Sheet 1 OUT PUT INVENTORS: $323 Aug. 24, 1926. 1,597,323

J. MASSOLLE ETAL DIFFERENTIAL MODULATOR Filgd March 30. 1921 3 Sheets-Sheet 2 INVENTORS:

/YMSSDLLI? Ala/vs Vosr 065E; lE/vaL By W Aug. 24, 1926.

IN PUT IN PUT 1,597,323 J. MASSOLLE ET AL DIFFERENTIAL MODULATOR Filed March 30 1921 3 Sheets-Sheet 5 (/OSEF HEM Mada/cling Sobrqe INVENTORS:

Patented Aug. 24, 1926.

UNITED STATES PATENT OFFICE.

J'OSEPH MASSOLLE, OF BEBLIN-GRUNEWALD, HANS VOG'I, OI BERLm-WILKEBSDOBI', AND JOSEF ENGL, OI BERLIN-GBUNEWALD, GERMANY, ASSIGNOBS TO TBI-EBGON LIMITED, 01' ZURICH, SWITZERLAND.

DIFFERENTIAL uonuna'ro'n.

Application fled larch 80, 1981, Serial No. 457,187, and in Germany Iarch 3, 1810.

ful manner.

Another object of the invention is the provision of arrangements such that alternating currents differing in phase from each other will flow in a air of similar circuits, these two circuits belng coupled to a third circuit in such a manner that a resultant current will normally flow in the third circuit, to-,

gether with means for varying the phase difference between the currents in the first two circuits in a desired manner so as to correspondingly alter the current in the third circuit. 7

In orderthat the invention may be clearly understood, we will proceed to describe the same with reference to the "forms -of'construction shown by way of example in the accompanying drawing, wherein Figs. 1 and 2 show diagrammatically differential connections according to this in- 86- vention.

lating to the connections shown by Figs. 1 and 2.

Figs. 4 and 5 show other modes of connection.

The tube B (Fig. 1) used as a generator produces high-frequency vibrations of constant am litude in the high-frequency circuit S. oupled to this circuit are two circuits D and D called differential circuits which are electrically exactly equivalent. They both take equal energy from the generating circuit S. Given exact-electrical equivalency of D -and D,, the current phases 0 both circuits are in resonance, but their effects upon the circuit K, which is coupled to circuits D and D neutralize each other as they are displaced the one with regard to the other by 180 (Fig. 3) When the electrical equality or balance of the circuits D and D is disturbed 'theirrespective current phases will be displaced the one with regard to the other and their differential effect will be transmitted to the circuit K. By op ite alteration of the capacity of D and 2 the current phases of the two circuits will be shifted for example in opposite directions. If, one phase is shifted for +90 and the other for 90, their effects on K will be in the same direction and they add themselves to produce the resultant Rb (Fig. 3). The alteration in the capacity necessary for this effect is small, so that the alteration in frequency of the circuits is not considerable. In Fig. 1 we have indicated diagrammatically variable capacities in circuits D and D to illustrate the principle of the invention, rather than any specific embodiment thereof. These capacities may be varied in correspondence with sound vibrations or otherwise, to modify the resultant effect in circuit K as stated. They may be varied, for example, by means of a condenser, which has one of its plates formed as a diaphragm, to constitute a condenser microphone, the diaphragm of which will vibrate in rhythm with acoustic vibrations received thereby, so that the capacity of the condenser microphone will vary correspondingly. A single condenser microphone may thus be connected to affect both circuits D and D,, as is indicated in Fig. 2. This method of connection oifersthe advantage that the condensers can be constructed for bilateral Figs. 3 3", 3 are diagrams of curves reaction, the membrane forming the common plate for the two condensers, as can be seen from Fig. 2. In this manner the advantage is ensured that the membrane is free from electro-static attractions, and may therefore be made so light that it can perfectly follow the acoustic vibrations. If the differential circuits are so disposed that, when the membrane is at rest, their effect on the circuit K is zero, the acoustic frequency is doubled since the membrane makes a deflection in each direction for each acoustic fre uency, and produces in circuit K, by each'de ection, an increase and decrease of the high frequency amplitudes while only single increases and decreases of the amplitudes should take place. For the purpose of speech reproduction, etc., it is therefore necessary to so untune the circuits D and D,

that their current phases are displaced from the outset, with relation to one another, by 90 (Fig. 3). The current curve of circuit K at a state of rest corresponds then to the resultant Re, whose ener is half that of the resultant energy at p ase equality according to Fi 3*. The variations 1n the capacity of t e microphone at maximum acoustic amplitudes are such that the phase displacement varies between 0 and 180 (Figs. 3 and 3"). The amplitude of the high frequency energy of the circuit 1s then controlled by the acoustic vibrations between 0 and a maximum value.

In the method for the transfer of low freuency vibrations to the amplitude of high frequency vibrations which has just been described, the dependence of thecurrent phase in oscillating circuits with forcedexcitation upon the resonance device is utihzed to transfer acoustic vibrations by means of a condenser microphone to the amplitude of the high frequency current.

The connection ereinbefore described can however be improved so that it permits the transfer of low frequency alternating currents of any origin to the high frequency amplitude.

As shown by Figs. 4 and 5 the high frequency circuits D and D which have caacity and inductance (ai 7nd,, ed, and cd d 8d act in difierentlal coupling on the circuit K, which has the inductances and caacity 70,, I0 and 07:. Condenser ck may be omitted if circuit K is to be aperiodic. Circuits D and D are fed preferably with uniform intensity, by means of the circuit S, which may be an undamped high frequency generator, across the self inductions a and 8,. K is then currentless so long as D and D are tuned to the same wave. The slightest disturbances of the tuning of D and D in opposite directions effect a proortionate, but with sufficiently small damp- 1ng relatively great, displacements of the current phases in D and D whose difference becomes effective in K.

The alteration of the tuning in the ryhthm of the low frequency alternating current to be transferred is effected according to the invention by means of iron choke coils E and E (Fig. 4) or E (Fig. 5). These are provided with high frequency windings h and 71/2 which are inserted in the differential circuits by being mounted in parallel or in series and which determine the natural wave length of the differential circuits. As is well known, the influence of the iron upon theself-induction of the windings depends on the degree of its magnetic saturation. In consequence of this, in the case of non-saturated iron the self induction of the high frequency winding is considerably greater than inv the case of iron which has been saturated. An alteration of the saturation by means of the superimposed low frequenc current brings about consequently an a teration of the self-induction of h, t id h and thereby dis lacements of the current bases in D an D which, when they are in opposite directions, cause the production of a high fre uency current in K, whose height of amp itude corresponds with the characteristic of the low frequency current. The transferring of the low frequency current 6 to the iron rings takes place across the windings 'w and w Fig. 4:, and '10, Fig. 5. In order to effect opposite alterations of the self-induction of h, and k by means of this current a suitable premagnetization of the iron cores is necessary. For this purpose, for example, the source of direct current cg is used which, by means of the windings g and 9,, produces such a magnetic flux in the iron rings that the low frequency current 6 causes an increase of the flux in one of the rings and a decrease in the other. In order to prevent the flow of alternating current in the circuit cg-g 2 caused by the coupling of the same with the alternating current windings, it is recommended that a resistance am be inserted in this circuit which may be either an inductive resistance or an ohmic resistance. The same applies to the low frequenc circuit, if its resistance is.

too feeble for t e coupling with the high frequency circuit. 7

As the greatest change of the self-induction takes place at the magnetizing knee, or elbow, (of the characteristic curverepresenting variations in intensity of magnetic flux in relation to the variations of magnetizing current,) it is an advantage to extend the premagnetization of the iron by means of source e. g., as far as the middle of the knee.

Furthermore, irons with the sharpest possible I knee are to be recommended. If the low frequency currents to be transferred must not be allowed to undergo a doubling of frequency, it is necessary to adjust D and D at a mean phase displacement; This can be effected by means of a suitable selection of the capacity and inductance of D and D (including it, and 7a,.) and also by the appropriate adjustment of the previous mag netization (different numbers of ampere turns for g, and 9 or the superposition of a suitable direct current voltage in the low frequency circuit).

The low frequency currents to be laid on may be of various kinds, as for example,

acoustic-electric currents, which can be pro- 1 duced with the aid of any microphone which quency currents which are thusinduced, can be employed directly for the wireless telephony, or for other purposes, such as for exam le the photographic recording of soun -phenomena, in which case an electrically operated source of light is employed for recording.

We claim r,

1. In difl'erential circuit devices, the combination of a pair of circuits having similar capacity and inductance, means for supplying alternating current equally thereto, the capacity-inductance products of said circuits being so adjusted in relation to each other that currents flowing therein will have a desired normal phase relation to each other, a third circuit so coupled with said first two circuits as to have a resultant normal current produced therein, and means for varying, as desired, the phase diiference between the currents in said two circuits, to

correspondingly alter the current in said third circuit.

2. In differential circuit devices, the com bination of a pair of circuits having similar capacity and inductance, means for supplying alternating current equally thereto, the capacity-inductance products of said circuits being so adjusted in relation to each other that currents flowing therein will have a desired normal phase relation to each other, a third circuit so coupled with said first two circuits as to have a resultant normal current produced therein, and means for with said first two circuits as to have a re. sultant normal current produced thereln,

and means for varying, as desired, the hase difference between the currents in sai two circuits, to correspondingly alter the current in said third circuit.

4. In differential circuit devices, the combination of a pair of circuits having similar capacity and lnductance, means for supplying alternating current equally thereto, the capacity-inductance products of said circuits being so adjusted as to cause a normal phase difference of 90 degrees: between the currents flowing therein, a third circuit so coupled with said first two circuits as to have a resultant normal current produced therein,

and means for varying the phase difference between the currents in said two circuits in correspondence with sound vibrations, to

correspondingly alter the current in said third circuit.

5. In differential circuit devices, the com bination of a pair of circuits having similar capacity and inductance, means for supplying high frequency alternating current equally thereto, the capacity-inductance products of. said circuits, eing so adjusted in relation to each other that currents fiowing therein will have a desired normal phase relation to each other, a third circuit so coupled with said first two circuits as to have a resultant normal current produced therein, and means for relatively varying the capacity-inductance products of said first two circuits in correspondence with sound vibrations.

6. In difierential circuit devices, the combination of a pair of circuits having similar capacity and inductance, means for supplying high frequency alternating current equally thereto, the capacity-inductance products of said circuits being so adjusted in relation to each other that currents flowing therein will have a desired normal phase relation to each other, a third circuit so coupled with said first two circuits as to have a resultant normal current produced therein, and means for relatively varying the inductances of said first two circuits in correspondence with sound vibrations.

7. In differential circuit devices, the combination of a pair of circuits having similar capacity and inductance, means for supplying high frequency alternating current equally thereto, the capacity-inductance products of said circuits being so adjusted in relation to each other that currents flowing therein will have a desired normal phase relation to each other, a third circuit so cou- 105 pled with said first two circuits as to have a resultant normal current produced therein. and means for relatively varying the capacity-inductance products of said first two circults at relatively low frequency. 7

8. In difl'erential circuit devices, the combination of a pair of circuits having similar capacity and inductance, means for supplying alternating current equally thereto, the

capacity-inductance products of said 'cirproducts of said circuits being so adjusted in relation to each other that currents flowin therein will have a desired normal phase 7 re ation to each other, a third circuit so conpled with said first two circuits as to have a resultant normal current produced therein, the inductances in said first two circuits having iron cores, means for maintaining the magnetization of said cores at a desired point, and means for relatively varying the magnetization of said cores as desired, to thereby relatively vary the induetances of said first two circuits.

' 10. In differential circuit devices, the combination of a pair of circuits having similar capacity and inductance, means for supplying high frequency alternating current equally thereto the capacity-inductance products of said circuits being so adjusted in relation to each other that currents flowing therein will have a desired normal phase re ation to each other, a third circuit so coupled with said first two circuits as to havea resultant normal current produced therein, the inductances in said first two circuits having iron cores, means for maintaining the magnetization of said cores at a desired point of saturation, and means for rela-. tively varying the magnetization of said cores in correspondence with sound vibrations.

In testimony whereof we aflix our signatures.

JOSEPH MASSOLLE. HANS VOGT. DR. JOSEF ENGL. 

